Computing devices, such as notebook computers, personal data assistants (PDAs), mobile communication devices, portable entertainment devices (such as handheld video game devices, multimedia players, and the like) and set-top-boxes (such as digital cable boxes, digital video disc (DVD) players, video cassette recorders, and the like) have user interface devices, which are also known as human interface devices (HID), that facilitate interaction between the user and the computing device. One type of user interface device that has become more common is a touch-sensor device that operates by way of capacitance sensing. A touch-sensor device usually is in the form of a touch-sensor pad, a touch-sensor slider, or touch-sensor buttons, and includes an array of one or more capacitive sensors. The capacitance detected by a capacitive sensor changes as a function of the proximity of a conductive object to the sensor. The conductive object can be, for example, a stylus or a user's finger.
In a touch-sensor button, a change in capacitance detected by a sensor due to the proximity of a conductive object can be measured by a variety of methods. Regardless of the method, usually an electrical signal representative of the capacitance detected by the capacitive sensor is processed by a processing device, which in turn develops electrical signals representative of the presence of the conductive object in proximity to the touch-sensor button.